Initial brushable trellis chart

Deselecting areas, applying filters, and broadcasting filters are not
implemented yet.
Switch zip submodule from https:// to git://
Pass brushG to redrawBrush

d3.select(this) is wasteful and not always reliable
Apply filters from trellis brushes

No broadcasting functionality yet.
Fix brush call, remove debugging output
Trellis external filtering and broadcasting

This also adjusts the method for comparing filters, allowing a chart to
define a "filterCompare" method that will be used to compare filters if
available.
This finally removes the date chart special case for setting filters.

Array instance checking will now use foo instanceof Array instead of
typeof(foo) == "array", which was unreliable (sometimes it's "object").

Trellis chart brush containers will now redraw the brush when set
externally.

renderBrush no longer takes brushG as a parameter. I'm not sure what I
was thinking when I made it so.

The deselected area will not yet fade.

The trellis chart still requires substantial refactoring and consistency
fixes; I'm not sure that the parameter specifications are currently
correct.